Students will launch the Number Detectives project by investigating mystery library checkout totals, trying place-value-based strategies, and recording early questions about how to solve large-number problems accurately.

Students will plan and test a math investigation using library checkout totals, choose and justify strategies for solving three-digit problems, document evidence with models and equations, and improve their method through peer critique before a teacher conference checkpoint.

Students will present their library checkout investigation to an authentic audience, explain and defend their three-digit addition and subtraction strategies with evidence, complete a brief conference-based performance check, and reflect on how feedback and error correction improved their final work.